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Wednesday, July 16, 2008

Quality Planning Techniques: Design of Experiments

How do you determine the way a material, product, or process affects your project? You can use a quality planning technique called design of experiments. This analytical technique can help you uncover which variables have the most influence on an outcome, and verify the capability of materials, products, and processes.

Most organizations want to improve their products and services. Designing experiments that verify these improvements is worth the time and effort put into them, since they are helpful in solving chronic quality problems. Properly designed experiments can help you:

eliminate re-work

achieve higher productivity

improve customer satisfaction

prevent problems

reduce extra inspections.

Design of experiments is more efficient and less disruptive than a trial method experiment. It also requires extra thought and planning, as a mistake during any part of the experiment can invalidate the entire analysis.

The objective of a designed experiment is to study specific outcomes by analyzing the impact of several variables at one time. Testing more variables at one time makes this process more efficient.

Whether you are searching for the root cause of a quality problem or you want to improve quality results, design of experiments is a beneficial technique for quality planning. In addition to the benefits listed above, it provides the following two important benefits.

Smaller sample sizes. This technique requires smaller sample sizes to receive the same accuracy of results.

Interaction between variables. It determines interactions between process variables. Certain combinations of variables can have a greater impact on the outcome than any one variable on its own.

Design of experiments is a technique that is most often applied to the product of a project. For example, pharmaceutical companies often perform designed experiments to test the composition of their drugs. If studying the XYZ drug, a designed experiment would have a matrix of experiments that tests X, Y, and Z in different amounts at the same time. The experiment would examine X1Y1Z1, X2Y1Z2, X1Y2Z3, and other such combinations. This experiment tests multiple variables at the same time.

In summary, design of experiments verifies how a material, product, or process is affecting your project. This quality planning technique is usually applied to projects that produce a product.